The objectives of this project are: 1) To concentrate and purify the listeria-sterilizing factor(s) generated by macrophages from macrophage-lymphocyte-mitogen cultures in vitro, define the optimal conditions for its production and study the conditions influencing its anti-listeria in vitro. 2) To test the spectrum of in vitro antimicrobial activity of this factor(s) against other Gram-positive bacteria, especially mycobacteria, and Gram-negative bacteria, e.g. various strains of Brucella abortus. 3) To determine whether or not the macrophages of other species of mammals, rabbit and man, in particular, can be stimulated to generate this or similar antimicrobial materials and under what experimental conditions.